Double-base propellant containing an aromatic hydroxy compound

ABSTRACT

1. In a double base plastisol type propellant containing nitrocellulose and liquid nitrate esters in combination with between 0.5 and 2.0 percent by weight of either 2,4-tolylene diisocyanate or hexamethylene diisocyanate based on the weight of said propellant, the improvement consisting in the incorporation of between 0.5 and 2.0 percent by weight of an aromatic hydroxy compound based on the weight of said diisocyanate, thereby rendering said propellant homogeneous and void-free, said aromatic hydroxy compound selected from the group consisting of 1,3-DIHYDROXY BENZENE, 1,2-DIHYDROXY BENZENE, 1-METHYL-3,5-DIHYDROXY BENZENE, 1,4-DIHYDROXY BENZENE, 1,2,3-TRIHYDROXY BENZENE, 1,3,5-TRIHYDROXY BENZENE, 1,3-DIHYDROXY-2-NITRO-BENZENE, 1-HYDROXY-3-ACETO-BENZENE, 1,3-DIHYDROXY-2-METHYL BENZENE, 1-METHANOL-2-HYDROXY BENZENE, AND 1,3-DIHYDROXY-2,4-NITROSO-BENZENE.

United States Patent iwi Stack l l May 20, i975 I DOUBLE-BASE PROPELLANT Primary E.t'umt'nerStephen J. Lechcrt, Jr.

CQNTMNING AN ARUMATIC HYDRQXY Attorney, Agent. or Hum-Nathan Edclherg; Robert P, COMPOUND Gibson; A. Victor Erkkilla [75] Inventor: Joseph 5. Stuck. Rivcrdale. NJ. [73] Assignee: The United States of America as EXEMPLAR CLAIM represented by the Secretary 0| the I. In a double base plastisol type propellant containing Armlh wufihinglom nitrocellulose and liquid nitrate esters in combination I23] pilcd: Apt 6 with between 0.5 and 2.0 percent by weight of either 2.4-tolylcne diisocyanate or hexamcthylcne dllSOC \'ill l PP Nil-1 nutc based on the weight of said propellant. the improvement consisting in the incorporation of between 521 U.S CL I V A D aun 49 9 49 3 and 2.0 PCI'CCI by Wfiighl Of an aromatic hydfl \y g 2; compound based on the weight of said dllSOCyLtflfllL. si Int. Cl Com: 5/00 hcmby said hmmgmwus [58 new 0' Search 49,94 95 96 98 I9 void-free. said aromatic hydroxy compound selected M9138. ion, 42, 44, ill. I9, 20. V9.8. 76.92 [mm "'9 l,3-dihydroxy benzene. l.2-dihydroxy benzene. [56] References Cited l-methyl-3.5-d|hydroxy benzene.

lcnc'. Mmlttln Ill/WM llarr t4t/l9 2 3 ih benzene :(lagcl et :tli 3 5 .i hcnzenc. 'HWI'L'HL' J C a .L 1.2mm; llll hfi Winkler l-t9/l9 x 1iff "et :45am 4mm Klager ul al. l49ll9 Y mutant mum Win ct al. l-t9ll9 3.296.043 uwm Fltlltt. t.\ al l49/l9 q y bcfllencl.3-dihydroxy-2.4-nitroso-hcnzcnc.

l6 Claims, 2 Drawing Figures IENI R GA IR Fm R P 2 m El imp-ma JOSEPH S STACK I DOL'llLl-l-llASl-l IRUPELLAXT CONTAINING AN AlttlhlXl'lC lll'lllttlXY L'UMPUl'ND This invention relates to a porous l'rcc \lilSt C \lllllllC treated nitrocellulose l asctl plastisol propellant.

In the past. one of the major disadvantages of con t-cntional composite nitrocellulose based plastisol type propellants \;trthe trtal ilits to be procured in a variety of l'ormulations lt \';t.\ found that such systems. which had favorable rttccltattical properties over a wide range ol temperature curcrncs. could only be formulated over a narro range of ratios llh respect to their ingredients. As a result. the variet ol' fortttulatiolts which could he prepared of a system containing a specific inrctlicttt such as a high energy casting solvent was very much limited W hen the :rl m c stettts were crosslittkcd with diisoct'aitate containing materials. the operating range over which the propellant exhibited favorable mechanical properties was cspanded considerably. It was apparent that the diisocyanatc treatment created a versatility of formulations for the corttposite nitrocellulose based plastisol systems which heretofore could not be achieved with conventional systems which were untreated.

As a further extension of the above. it was found that diisoeyanate containing compounds were quite useful in the improvement of the physical properties of the nitrocellulose based plastisol propellants. It is thought that this is due to the reactivity of the ,diisoeyanate containing material with such propellant ingredients as nitrocellulose. amines. and the hydroxy containing compounds. As a result of this action. the physical properties at the propellant such as elongation and tensile strength are improved to a degree beyond that of the base propellant. This is quite useful because. as an example. castaltle case-bondable nitrocellulose based plastisot propellants are desired which possess adequate elongation at low temperatures in order to Withstand the thermal stresses created between the propellant and the rocket motor case. Further. propellants with sufficient rigidity and strength at high temperatures. such as the above diisocyanate treated propellant. are necessary to prevent damaging deformation of the propellant during storage and firing.

However. even though the treatment of nitrocellulost: based plastisol propellants with diisoeyunate containing materials is accompanied by improvement in physical properties. there is one serious problem. The diisocyanate containing materials in use today are highly reactive with water. They react with even trace amounts of moisture present in the composite doublebase propellant to produce carbon dioxide which. in turn. leads to the formation ol a porous system during subsequent processing and curing of the propellant. Thus. a propellant is produced which possesses a multitude ot \oid-likc pttt'cs. As a practical matter. it has thus been l tltld tlll rltjtlll to duplicate or control the hunting characteristics of a porous diisocyanate treated nitrocellulose based pla tisol propellant. As a result. this adu-rsel atl'ccl the reliability of the ballistics 2 characteristics of the propellant. However. it has been found that. in some cases. void free and homogeneous propellants might be prepared by employing mcticulous drying and handling of ingredients and tedious procedures to avoid the presence of water in the system. As is apparent. such techniques are highly danger ous. Thus. in view of the above. the propellant formulator is confronted with a dil'l'tcult problem when processing such propellants by standard processing techniques.

This invention provides the needs of the art. as heretolore set forth. by a simple technique which allows the production of void-free diisocyanate treated nitrocellulose based plastisol. with their attendant advantages b existing facilities and operating procedures.

An object of this invention is to provide a homoge nous. porous tree. diisocyanate treated nitrocellulose based plastisol propellant.

Another object is to provide the propellant described by existing facilities and operating procedures.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying pictorial showin wherein:

FIG. I is a pictorial view of a conventional diisoeyanate treated nitrocellulose based plastisol propellant.

FIG. 2 is a pictorial view of the formulation of FIG. I which has been modified in accordance with this invention.

It has now been discovered that if a slight amount of an aromatic hydrotty containing compounds such as l.3-dihydroxy benzene. otherwise known as resorcinol. is added to the propellant during processing. a homogeneous porous free diisoeyanate treated nitrocellulose based plastisol propellant may he produced utilizing conventional facilities and operating procedures. The grain structure of such a propellant is illustrated in the photograph of FIG. 2. However. in contrast. as shown in the photograph of FIG. 1. the grain structure of the conventional diisoeyanate treated nitrocellulose based plastisol propellant produced by the same procedures is non-homogeneous and has a multitude of void-like spaces throughout its mass. This is clearly an achievemerit in view of the fact that conventional procedures are utilized throughout the treatment of the propellant with both the diisoeyanate containing material and the aromatic hydrotty compound.

The aromatic hydrotty compounds which may be utilized in this invention to give results comparable to I .3- dihydroity benzene include: LZ-dihydroxy benzene; lmcthyl 3.5-dihydrotty benzene: l.4-dihydroxy benzene; l,2.3-trihydroxy benzene; l.].5-trih vdrosy henzene'. l.3-dihydroxy 2 nitro-benzene; l-hydroxy 3- acetobenzene'. l.3-dihydroxy 2-mcthyl benzene; l methanol -2-hydroxy benzene. and l.3-dihydroxy 2.4- nitroso-benzene. All of the above aromatic hydrmty compounds give similar results when utilized to modify the diisocyanate treated nitrocellulose based plastisol propellant.

Typical nitrocellulose based plastisol propellant l'or mtilations embodying the concept of this invention include the following set forth in Table l below TABLE I INURHNFNTS lit. to

TABLE l ot\tinned INGRliDll-K lh l I 1 4 S h Ammonium Perchlorate. 507-! 2|, 2|." 1|.U 2L0 11.0 21.0 Resorcmol. added 2.0 2.0 2.0 2.0 1.0 LU lA-lol lcnediisocyanate. Idtktl L14 L47 L62 L17 2J5 2.38 Casting Solvent ill 49.5 46. 44.5 42.5 31.5 33.5 Ponder/Solvent Ratio (1.13 0.41 (1.49 0.556 0.77 0.99 NOTE: Percent y Weight t llus slltnlls of "all Powder IISQ t I) Illl (2) lat Nitrocellulose. l2 h'iN.- 50.0 74.0 lb) Ntltughhict'itt lLU 24,0 t Illtrnnlipht'lttlllll'llltC 2.0 1.0

Casting Solient X I l Percent by weight tat [methylene glycol tltnitrate 65' Uutane Tirol 'l'rimtrate 1d? 1 mtnultphettylaminc I;

The formulations set forth above all exhibit the improvement ol mcchanical properties heretofore described in connection with the crosslinking of the base propellant with a diisocyanatc containing material. In addition. the final cast of the composites set forth in Table l all rescttible the pictorial view set forth in FIG. 2 in that they are homogeneous and void free. All of the above formulations were processed in accordance with the procedure set forth in Example I below:

EXAMPLE I The lluid hall powder and resorciitol is added to the casting solvent dehydrated to a moisture content of approxitttately tl.l percent and is left at about 7UI5F for about It hours. At the end ol'this period. the aluminum and ammonium perchlorate ingredients are added to the resulting solution accompanied by agitation. To the ahovcothe diisocyanate containing material is added and the mass is mixed for about l hour under a vacuum M4 to ill mm of mercury. The mass is mixed until a viscosity of .ltLttttll to 40.000 centipoise is reached at which time the mass is cast into the desired molds and cured at 60C for 3 days.

Although there are many diisocyanatc containing materials which may be utilized to modify the nitrocellulose based plastisol propellant. the most common are 2.4-tolylene diisocyanate and hexamethylene diisocyanatc. In general. the antounl of diisocyanate containing material utilized in the treatment of the described composite propellant may vary from 0.5 to 5.0 percent by weight based on the weight of the propellant. Generally. the amount of diisocyanate containing materials utilized in the system varies with the amount of nitrocellulose in the propellant. The most efl'ective concentration of diisocyanate containing material has been found to be between 0.5 and 3.0 percent. In the latter range. the modified or cross-linked nitrocellulose based plastisol propellant exhibits exceptional improvement in mechanical properties consistent with the desired degree of homogeneity. At concentrations of less than 0.5 percent. there is only marginal improvement in the mechanical properties when contrasted to the uncross linked propellant composite. At concentrations olovcr 3.0 percent. the propellant tends to exhibit embrittlement as a result of the high degree ofcrosslinking ol' the propellant. In addition. the propellant may have a nonhomogencous appearance. As noted. the crosslinlting agent aries with the amount of nitrocellulose in the propellant. In the composites set forth in Table l. the lmll ponder contains betneen 74 and 90 percent by TABLE ll Diitioeyanate Aromatic llytlroi Com ound 0.! 0.75 0.5 Ole-L5 tit-t5 l.$ 2.0 :.u 2. 1.

All figures represent per cent by weight.

The above table sets forth the amount of aromatic hydroxy compound utilized in a propellant system based on the amount of diisocyanate containing mate rial utilized to crosslink the propellant composite. ll an amount of hydroxy compound below 0.5 percent is uti lized. the propellant will exhibit a low degree of elonga' tion and high degree of tensile strength. However. the overall system will be void free but thermal stability will be borderline. At hydroxy compound concentrations of L0 to L5 percent. the propellant systems are void free accompanied by reasonably good mechanical proper ties and good thermal stability. At the 2.0 percent concentration of the hydroxy compound. the optimum in mechanical properties and thermal stability is obtained with the treated propellant system. It amount above 2 percent is utilized. the propellant exhibits a low degree of tensile strength and a high degree of elongation. It has been found that Within the range indicated. the overall stability of the propellant is excellent and the treated propellant is homogeneous and void l'ree.

As is evident from the above. aromatic hydrox compounds. when employed in small concentrations in the describedplastisol type propellants. control the gassing of carbon dioxide which is normally associated with systems cross-linked with 2.4tolylcne and hcxamethylcne diisocyanate. As a result. it is now possible to prtv cess homogeneous and void free composite nitrocellulose based plastisol propellant under non-rigidly con trolled environments and without meticulous drying of special ingredient in the composite.

Obviously. there are many modifications and varia. tions of the prsent invention which are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims. the invention ma he practiced otherwise than as specifically described.

I claim:

1. in a double base plastisol type propellant contain ing nitrocellulose and liquid nitrate esters in combination with between 0.5 and 2.0 percent by weight of either 2.4-tol vlene diisocyanate or hexamethylene diisocyanate based on the weight of said propellant. the improvement consisting in the incorporation of between 0.5 and 2.0 percent by weight of an aromatic hydroxy compound based on the weight of said diisocyanate. thereby rendering said propellant homogeneous and void-free. said aromatic hydroxy compound selected from the group consisting of .3-dihydroity benzene.

.Ldihydroxy benzene. -methyl-.L$-dihydroxy benzene, .-'l-dihydroxy benzene. .ZJ-trihydroev benzene. .lS-trihydroxy benzene. .LdihydroxyZ-nitro-benzene. -h \'drox -aceto-henzene, -J-dihydroxy-2-methyl benzene. -metltanol-Z-hydrosy benzene. and .S-dihydroxy-ZA-nitroso-bcnzene.

1. In the propellant of claim I wherein said diisocyanate is present in an amount between 0.5 and 0.75 percent by weight. the improvement wherein said propellant is modified with 0.5 percent by weight of said arornatic hydrot compound.

3. ltr the propellant of claim l wherein said diisocyanate is present in an amount between 0.76 and L5 percent by weight. the improvement wherein said propellant is modified with between H) and l.5 percent by weight of said aromatic hydroxy compound.

4. In the propellant ol'claint I wherein said diisocyunate is present in an amount between LS and 2.0 percent by weight. the improvement wherein said propellant is modified with 2.0 percent by weight of said aromatic hydroxy compound.

5. In the propellant of claim I wherein said diisocyanate is present in an amount of 2.0 percent by weight. the improvement wherein said propellant is modified with 2.0 percent by weight of said aromatic htdroxy compound.

6. In the propellant 0! claim I. the improvement wherein said propellant is modified with l .J-dihydroxy benzene.

7. In the propellant of claim I. the improvement wherein said propellant is modified with l .Z-dihydrmty benzene.

8. In the propellant of claim I. the improvement wherein said propellant is modified with l-meth vl-3.5- dihydroity benzene.

9. In the propellant of claim 1, the improvement wherein said propellant is modified with l .4-dilzydroxy benzene.

[0. In the propellant of claim I, the improvement wherein said propellant is modified with l.2..1- trihydroxy benzene.

II. In the propellant of claim I. the improvement wherein said propellant is modified with I15- trihydroxy benzene.

12. In the propellant of claim I. the improvement wherein said propellant is modified with l .f -dihydroty 2-nitro-bertzene.

l3. In the propellant of claim I. the improvement wherein said propellant is modified with t-hydroty-fiaceto-benzene.

14. In the propellant of claim l. the improvement wherein said propellant is modified with t- ,t-dih drot Z-methyl benzene.

[5. In the propellant of claim l. the ttttprotement wherein said propellant is modified with l-ntethanol-L hydroxy benzene.

Hi. In the propellant of claim I. the improvement wherein said propellant is modified with LJ-dih droxy 2.4-nitroso-benzene.

t t i O 

1. IN A DOUBLE BASE PLASTISOL TYPE PROPELLANT CONTAINING NITROCELLULOSE AND LIQUUID NITRATE IN COMBINATION WITH BETWEEN 0.5 AND 2.0 PERCENT BY WEIGHT OF EITHER 2,4-TOLYLENE DIISOCYANATE OR HEXAMETHYLENE DISSOCYANATE BASED ON THE WEIGHT OF SAID PROPELLANT, THE IMPROVEMENT CONSISTING IN THE INCORPORATION OF BETWEEN 0.5 AND 2.0 PERCENT BY WEIGHT OF AN AROMATIC HYDROXY COMPOUND BASEDON THE WEIGHT OF SAID DIISOCYANATE, THEREBY RENDERING SAID PROPELLANT HOMOGENEOUS AND VOID-FREE, SAID AROMATIC HYDROXY COMPOUND SELECTED FROM THE GROUP CONSISTING OF 1,3-DIHYDROXY BENZENE, 1,2-DIHYDROXY BENZENE, 1-METHYL-,5-DIHYDROXY BENZENE, 1,4-DIHYDROXY BENZENE, 1,2,3-TRIHYDROXY BENZENE, 1,3,5-TRIHYDROXY BENZENE, 1,3-DIHYDROXY-2-NITRO-BEMZENE, 1-HYDROXY-3-ACETO-BENZENE, 1-3-DIHYDROXY-2-METHYL BENZENE 1-METHANOL-2-HYDROXY BENZENE, AND 1,3-DIHYDROXY-2,4-NITROSO-BENZENE.
 2. In the propellant of claim 1 wherein said diisocyanate is present in an amount between 0.5 and 0.75 percent by weight, the improvement wherein said propellant is modified with 0.5 percent by weight of said aromatic hydroxy compound.
 3. In the propellant of claim 1 wherein said diisocyanate is preSent in an amount between 0.76 and 1.5 percent by weight, the improvement wherein said propellant is modified with between 1.0 and 1.5 percent by weight of said aromatic hydroxy compound.
 4. In the propellant of claim 1 wherein said diisocyanate is present in an amount between 1.5 and 2.0 percent by weight, the improvement wherein said propellant is modified with 2.0 percent by weight of said aromatic hydroxy compound.
 5. In the propellant of claim 1 wherein said diisocyanate is present in an amount of 2.0 percent by weight, the improvement wherein said propellant is modified with 2.0 percent by weight of said aromatic hydroxy compound.
 6. In the propellant of claim 1, the improvement wherein said propellant is modified with 1,3-dihydroxy benzene.
 7. In the propellant of claim 1, the improvement wherein said propellant is modified with 1,2-dihydroxy benzene.
 8. In the propellant of claim 1, the improvement wherein said propellant is modified with 1-methyl-3,5-dihydroxy benzene.
 9. In the propellant of claim 1, the improvement wherein said propellant is modified with 1,4-dihydroxy benzene.
 10. In the propellant of claim 1, the improvement wherein said propellant is modified with 1,2,3-trihydroxy benzene.
 11. In the propellant of claim 1, the improvement wherein said propellant is modified with 1,3,5-trihydroxy benzene.
 12. In the propellant of claim 1, the improvement wherein said propellant is modified with 1,3-dihydroxy-2-nitro-benzene.
 13. In the propellant of claim 1, the improvement wherein said propellant is modified with 1-hydroxy-3-aceto-benzene.
 14. In the propellant of claim 1, the improvement wherein said propellant is modified with 1-3-dihydroxy-2-methyl benzene.
 15. In the propellant of claim 1, the improvement wherein said propellant is modified with 1-methanol-2-hydroxy benzene.
 16. In the propellant of claim 1, the improvement wherein said propellant is modified with 1,3-dihydroxy-2,4-nitroso-benzene. 